eba (version 1.5-2)

linear2btl: Linear Coefficients To BTL Estimates

Description

Transforms linear model coefficients to BTL parameter estimates.

Usage

linear2btl(object, order=FALSE)

Arguments

object

an object of class glm or lm specifying a BTL model

order

logical, does the model include an order effect? Defaults to FALSE

Value

• btl.parameters
  a matrix; the first column holds the BTL parameter estimates, the second column the approximate standard errors
• cova
  the approximate covariance matrix of the BTL parameter estimates
• linear.coefs
  a vector of the original linear coefficients as returned by glm or lm

Details

The design matrix used by lm or glm usually results from a call to pcX. It is assumed that the reference category is the first level.

The covariance matrix is estimated by employing the delta method.

See Imrey, Johnson & Koch (1976) for more details.

References

Imrey, P.B., Johnson, W.D., & Koch, G.G. (1976). An incomplete contingency table approach to paired-comparison experiments. Journal of the American Statistical Association, 71, 614--623.

See Also

eba, eba.order, glm, pcX.

Examples

data(celebrities)
y1 <- t(celebrities)[lower.tri(celebrities)]
y0 <- celebrities[lower.tri(celebrities)]

## Fit BTL model using glm
btl.glm <- glm(cbind(y1, y0) ~ pcX(9)[,-1] - 1, binomial)
linear2btl(btl.glm)